(Chemical symbol: Cr). A lustrous, hard, very brittle, steel-gray metallic element used to harden steel alloys, to produce stainless steels, and in corrosion resistant plating. Melting point:1615°C (2939T); boilingpoint:2200°C(3992’F); atomic number: 24; atomic weight, 5.996.
Chromium is of great technical importance in metallurgy because of its hardening effect on steel, and because of its corrosion resistant properties. It is unaffected by the action of air at ordinary temperatures and is also resistant to chemicals.
A material containing chromium is difficult to weld because of the formation of chromium oxide. This oxide forms a coating on the surface during welding, but the coating can be removed by grinding or by using special fluxes.
Chromium is one of the basic ingredients used in producing stainless steels. As an ingredient in alloy steel, chromium is a hardening element which also tends to increase the strength of the steel. When the percentage is from 12% to 30%, chromium increases the corrosion and oxidation resistance of the steels; this holds true at both high and low temperatures. There is little loss of strength in chrome steels at temperatures up to480°C(900°F). See STAINLESS STEEL.